EP0660470A1 - Verfahren und Vorrichtung zur Emissionswellenlängenstabilisierung eines Lasers - Google Patents

Verfahren und Vorrichtung zur Emissionswellenlängenstabilisierung eines Lasers Download PDF

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Publication number
EP0660470A1
EP0660470A1 EP94119836A EP94119836A EP0660470A1 EP 0660470 A1 EP0660470 A1 EP 0660470A1 EP 94119836 A EP94119836 A EP 94119836A EP 94119836 A EP94119836 A EP 94119836A EP 0660470 A1 EP0660470 A1 EP 0660470A1
Authority
EP
European Patent Office
Prior art keywords
laser
gas
cell
waveguide
wavelength
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP94119836A
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English (en)
French (fr)
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EP0660470B1 (de
Inventor
Piero Gambini
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
OTC Optical Technologies Center SRL
Original Assignee
CSELT Centro Studi e Laboratori Telecomunicazioni SpA
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Publication date
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Publication of EP0660470A1 publication Critical patent/EP0660470A1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters
    • H01S5/0687—Stabilising the frequency of the laser
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
    • H01S3/1303—Stabilisation of laser output parameters, e.g. frequency or amplitude by using a passive reference, e.g. absorption cell

Definitions

  • the present invention refers to lasers, and, more particularly, regards a method and a device for stabilization of the emission wavelength of a laser, such stabilization being obtained by locking the emission wavelength to an absorption line of a gas.
  • the invention can be used for stabilization of the emission wavelength of a semiconductor laser acting as source in an optical communication system.
  • the laser emission wavelength is subjected to fluctuations and that, consequently, lasers are associated to control circuits to stabilize such a wavelength.
  • the stabilization must be absolute, i.e., independent from the environment, so that the source remains fairly stable both in the short and the long term and reproducibility of the emission wavelength is good.
  • Such applications include metrology (measurement of frequencies, lengths, etc.), wavelength division multiplexing, optical communications, where a stable and accurate wavelength reference must exist in order to control transmitters at different locations or to ensure correct identification of the various channels, etc.
  • absolute stabilization is obtained by locking the emission wavelength of the laser to an absorption line of a gas having an absorption spectrum with lines whose wavelength is near the emission wavelength of the source (typically, in a neighbourhood of 1.5 ⁇ m for optical communications applications).
  • Several techniques have been proposed to implement the locking; two examples are described by F. Bertinetto et al. in the papers: "Stabilization of the Emission Frequency of 1.54 ⁇ m DFB Laser Diodes to Hydrogen lodide" , IEEE Photonics Technology Letters, Vol. 4, No.
  • the radiation emitted by the laser is adequately modulated and sent into a cell containing the gas, the output radiation is detected, an error signal, representing the sign and the magnitude of the shift of the actual laser wavelength relative to the line wavelength (and thus to the nominal emission wavelength), is derived through a feed-back loop from the detected signals, and is fed to the laser control circuits. Transfer of radiation from the source to the cell and from the cell to the detector takes place in free space.
  • the purpose of the invention is to provide a method and a device for stabilization of the above type, in which the inconveniences arising from free space propagation of the radiation to be stabilized are eliminated.
  • a method is given in which the radiation to be stabilized is made to interact with the gas while it is guided along an optical waveguide traversing an environment containing the gas, the waveguide being such as to give rise to an evanescent field also propagating outside the waveguide.
  • An evanescent field is a time varying electromagnetic field whose field amplitude decreases very rapidly and monotonically. but without an accompnanying phase shift, in a particular direction, and without being due to absorption.
  • the device implementing the method includes means for sending the radiation emitted by a laser into a cell ccntaining a gas which has an absorption line at a wavelength near the nominal source wavelength, as well as means for detecting the radiation present at the cell output and for deriving an error signal from the signals resulting from the detection;
  • the sending means include an optical waveguide of which a portion is located inside the cell and which is connected to the detection means and has such guiding characteristics as to give rise to an evanescent field also propagating around it, thus ensuring interaction between radiation and the gas contained in the cell.
  • the optical waveguide guide is a "D" fibre.
  • Figure 1 shows the device according to the invention in the non limitative example in which the signal from the source to be stabilized is phase-modulated and the locking is done with respect to the peak of the absorption line, as described in the first of the two above mentioned papers of F. Bertinetto et al.
  • the invention is at any rate independent of the particular locking technique used.
  • thick lines represent optical waveguides and thin ones electrical connections.
  • the signal emitted by source 1 is sent to a fibre stub 2.
  • pig-tail means a short length of fibre connected to a device, e . g. a laser, to make its connection with another device or with a fibre easier.
  • the pig-tail is included into the source 1.
  • power splitting device 3 the signal is split into two parts, one part being the useful signal and the other being used for stabilization.
  • the latter part is sent to an optical phase modulator 4 driven by a radio-frequency signal provided by generator 5.
  • the phase-modulated signal is collected by a fibre 6 passing, for some of its length, inside a cell 7 filled with a gas having absorption lines which can be used for wavelength stabilization of source 1.
  • Fibre 6 enters or leaves cell 7 through apertures sealed with, for example, epoxy resin. Outside of cell 7, fibre 6 terminates on a photo-detector 8. whose output is connected in turn to mixer 9 which also receives signals from generator 5.
  • a phase-shifting device 10 between generator 5 and mixer 9 sets the correct phase relationship between the modulating signal and the cell output signal.
  • the mixer output is a signal whose amplitude and sign depend on the shift between the actual emission wavelength of laser 1 and the nominal wavelength; such signal, adequately filtered in loop filter 11, drives control circuits of laser 1 (integrated into the same block representing the source).
  • the signal output by filter 11 will adjust the laser injection current, or the temperature, or the position of a mirror, etc.
  • Fibre 6 is advantageously a "D" fibre.
  • a "D” fibre owes its name to the shape of its cross section.
  • cladding 12 of the fibre has a flat part, obtained by axially cutting the preform, and the core comes very close to the flat part.
  • the electromagnetic field thus presents tails (evanescent field) propagating in the environment around the fibre, which environment can thus affect a signal transmitted along the fibre itself. Therefore, by using such fibres, the interaction is obtained between the radiation emitted by source 1 and the gas contained in cell 7, as required for locking to an absorption line, even though propagation of the radiation is guided within the cell.
  • the system herein described eliminates the above mentioned inconveniences. Indeed, a fairly long fibre stub can be placed inside a cell 7 even of reduced size, so that there is a long region of interaction between radiation emitted by laser 1 and the gas in a limited room. Moreover, thanks to the fact that the radiation to be stabilized is guided from the source up to the detector, no optical misalignment occurs, and optimum mechanical stability of the device is ensured.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Semiconductor Lasers (AREA)
  • Lasers (AREA)
  • Spectrometry And Color Measurement (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
EP94119836A 1993-12-16 1994-12-15 Verfahren und Vorrichtung zur Emissionswellenlängenstabilisierung eines Lasers Expired - Lifetime EP0660470B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITTO930954 1993-12-16
ITTO930954A IT1272077B (it) 1993-12-16 1993-12-16 Procedimento e dispositivo per la stabilizzazione della lunghezza d'onda di emissione di un laser

Publications (2)

Publication Number Publication Date
EP0660470A1 true EP0660470A1 (de) 1995-06-28
EP0660470B1 EP0660470B1 (de) 1997-03-19

Family

ID=11411936

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94119836A Expired - Lifetime EP0660470B1 (de) 1993-12-16 1994-12-15 Verfahren und Vorrichtung zur Emissionswellenlängenstabilisierung eines Lasers

Country Status (5)

Country Link
EP (1) EP0660470B1 (de)
JP (1) JP2519672B2 (de)
CA (1) CA2138105C (de)
DE (2) DE660470T1 (de)
IT (1) IT1272077B (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1075063A2 (de) * 1999-08-05 2001-02-07 Agilent Technologies, Inc., a corporation of the State of Delaware Verfahren und Vorrichtung zur Stabilisierung der Wellenlänge eines Laers

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4608512B2 (ja) * 2007-03-30 2011-01-12 日本電信電話株式会社 周波数安定化光源

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
BERTINETTO F ET AL: "Stabilization of the emission frequency of 1.54 mu m DFB laser diodes to hydrogen iodide", IEEE PHOTONICS TECHNOLOGY LETTERS, APRIL 1993, USA, VOL. 5, NR. 4, PAGE(S) 472 - 474, ISSN 1041-1135 *
MUHAMMAD F A ET AL: "Sensitivity enhancement of D-fibre methane gas sensor using high-index overlay", IEE PROCEEDINGS J (OPTOELECTRONICS), APRIL 1993, UK, VOL. 140, NR. 2, PAGE(S) 115 - 118, ISSN 0267-3932 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1075063A2 (de) * 1999-08-05 2001-02-07 Agilent Technologies, Inc., a corporation of the State of Delaware Verfahren und Vorrichtung zur Stabilisierung der Wellenlänge eines Laers
EP1075063A3 (de) * 1999-08-05 2002-09-11 Agilent Technologies, Inc. (a Delaware corporation) Verfahren und Vorrichtung zur Stabilisierung der Wellenlänge eines Laers
US6574251B1 (en) 1999-08-05 2003-06-03 Agilent Technologies, Inc. Method and device for stabilizing the emission wavelength of a laser source

Also Published As

Publication number Publication date
DE69402168D1 (de) 1997-04-24
ITTO930954A0 (it) 1993-12-16
DE660470T1 (de) 1996-01-18
CA2138105A1 (en) 1995-06-17
EP0660470B1 (de) 1997-03-19
JPH07211977A (ja) 1995-08-11
DE69402168T2 (de) 1997-07-24
CA2138105C (en) 1999-03-30
JP2519672B2 (ja) 1996-07-31
ITTO930954A1 (it) 1995-06-16
IT1272077B (it) 1997-06-11

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